Electrically conductive gel and conductive human interfaces and electrodes formed using electrically conductive gel

ABSTRACT

A conductive human interface includes an insulating body of elastomeric material and a compliant electrode embedded in the insulating body. The electrode is formed from an electrically conductive gel including a polymeric material and conductive particles dispersed in the polymeric material. The conductive particles can be included in the gel in an amount that is not more than about 10% by weight.

BACKGROUND

The present specification generally relates to electrically conductive gel and, more specifically, to electrically conductive gel suitable for forming electrodes of conductive human interfaces for communicating signals with the skin of a user.

Conductive human interfaces can use electrodes to communicate signals such as, for example, Transcutaneous electrical nerve stimulation (TENS) signals, or Electromyographic (EMG) signals, with the skin of the user. In some examples the electrodes can be formed from metallic materials. Metallic electrodes can be stiff and rigid compared to human tissue. Thus, metallic electrodes can be unsuitable for long term usage.

Polymers have desirable mechanical properties. For example, polymers can be compliant and elastic, which can be desired when contacting the skin of a user. However, polymers are generally non-conductive. Conductive polymers can be formed by combining a polymer with a conductive material. However, conductive polymers typically suffer from one of two problems. Either the conductive polymer has an undesirably high bulk resistance, or the conductive polymer is too stiff or rigid for long term usage. Moreover, certain formulations of conductive polymer can be impractical to mold, which further limits their use.

As noted above, stiff and rigid electrodes can be undesirable for use as an electrical interface with the skin of a user for long periods of time, e.g., a full day of activity. For example, throughout the daily living activities of a user, the muscles and skin can move. Stiff and rigid electrodes can cause discomfort due to insufficient movement compared with the movement of the user. Additionally, the electrodes can lose direct contact with the skin, i.e., lift off from the skin. Lift off can result in the loss of signal communication with the skin.

Accordingly, a need exists for alternative electrically conductive gels, and conductive human interfaces for communicating signals with the skin of the user.

SUMMARY

In one embodiment, a conductive human interface can include an insulating soft coating, and one or more compliant electrodes. The one or more compliant electrodes can be embedded in the insulating soft coating. The one or more electrodes can be formed from an electrically conductive gel. The electrically conductive gel can include a polymeric material and conductive particles dispersed in the compliant material. The conductive particles can form between 2% and 6% of the electrically conductive gel by weight.

In another embodiment, a conductive human interface can include an insulating soft coating, and one or more compliant electrodes. The one or more compliant electrodes can be embedded in the insulating soft coating. The one or more electrodes can be formed from an electrically conductive gel. The electrically conductive gel can include a polymeric material and amalgamated carbon nanotubes dispersed in the compliant material. The amalgamated carbon nanotubes can be less than about 0.040 inches in size.

In another embodiment, an electrically conductive gel can include a polymeric material and a conductive additive. The conductive additive can be compounded with the polymeric material. The conductive additive can include conductive particles. The conductive particles can form between about 1% and about 10% of the electrically conductive gel by weight. A majority of the conductive particles can be between about 0.030 inches and about 0.050 inches in size. An Elongation at Break of the electrically conductive gel can be between about 50% and about 200%. The electrically conductive gel can have a bulk DC resistance of less than 1000 Ω-cm.

These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description, in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts a conductive human interface according to one or more embodiments shown and described herein;

FIG. 2 schematically depicts an exploded view of an interface system including a partial cross-sectional view of the conductive human interface of FIG. 1 along line 2-2 according to one or more embodiments shown and described herein;

FIG. 3 schematically depicts enlarged view 3 of the conductive human interface of FIG. 2 according to one or more embodiments shown and described herein;

FIG. 4 schematically depicts a conductive human interface according to one or more embodiments shown and described herein;

FIG. 5 schematically depicts a cross-sectional view of the conductive human interface of FIG. 4 along line 5-5 according to one or more embodiments shown and described herein;

FIG. 6 schematically depicts a conductive human interface according to one or more embodiments shown and described herein;

FIG. 7 schematically depicts a cross-sectional view of the conductive human interface of FIG. 6 along line 7-7 according to one or more embodiments shown and described herein; and

FIG. 8 schematically depicts a processing device according to one or more embodiments shown and described herein.

DETAILED DESCRIPTION

FIG. 1 generally depicts one embodiment of a conductive human interface for communicating signals with the skin of a user. The conductive human interface generally includes an insulating soft coating and one or more compliant electrodes formed from an electrically conductive gel. Various embodiments of the electrically conductive gel, the compliant electrodes, the conductive human interface, and their operation will be described in more detail herein.

Referring now to FIGS. 1, and 2, an embodiment of a conductive human interface 100 is schematically depicted. The conductive human interface 100 can be configured to communicate electrical signals with the skin of a user and act as a physical interface with the user. In some embodiments, the conductive human interface 100 can also be configured to interface with an assistive device. The assistive device can be any device supplemental to the body of a user that cooperates with the neuromuscular and skeletal system of the user such as, for example, a prosthetic device (e.g., a prosthetic socket), an orthotic device, an exoskeletal device, a powered wheelchair, or the like. Accordingly, while certain embodiments of the present disclosure relate to a prosthetic liner 102, the conductive human interface 100 can include the prosthetic liner 102, a sleeve, a band, a pad, or the like.

The conductive human interface 100 can include a fabric layer 110 configured to form a flexible substrate. The fabric layer 110 can include one or more fabric materials such as, for example, stretch controlling fabrics, stretchable non-woven materials, fiber-on-end fabrics, or the like. Stretch-controlling fabric can be more stretchable in one direction than another direction. For example, a stretch-controlling fabric can have a limited stretch direction that is substantially orthogonal to a non-limited stretch direction. Accordingly, when the conductive human interface 100 includes a prosthetic liner 102, the stretch-controlling fabric can be oriented to permit greater stretch in a circumferential direction than in a longitudinal direction (i.e., along the length of the prosthetic liner 102).

Referring now to FIG. 3, the fabric layer 110 can include an interior surface 112 and an exterior surface 114. The interior surface 112 can form a boundary with an insulating soft coating 120 configured for comfortable long term wear. As used herein, the term “insulating” can mean that a material can be classified as an electrical insulator, i.e., a material having sufficiently high resistivity to substantially prevent current flow when exposed to operating voltages of the device. The insulating soft coating 120 can be formed from materials having a hardness on the Shore 00 scale such as, for example, a hardness of less than about 75 on the Shore 00 scale in one embodiment, or a hardness of between about 15-35 on the Shore 00 scale in another embodiment. Accordingly, the insulating soft coating 120 can be formed from a soft polymer such as, for example, thermoplastic elastomers (TPE), silicones, block copolymers, urethanes, or the like. The insulating soft coating 120 can be elastic, which can be characterized according to the Elongation at Break of a modified ASTM standard D412. According to some embodiments, the insulating soft coating 120 can have an Elongation at Break of greater than about 500%, such as for example, between about 1,000% and about 2,000% in one embodiment, between about 1,250% and about 1,750% in another embodiment, or about 1,500% in a further embodiment. The thickness 122 of the insulating soft coating 120, as measured from the interior surface 112 of the fabric layer 110 to the contact surface 124 of the insulating soft coating 120, can be less than about 1 inch (about 25.4 mm) such as, for example, less than about 0.75 inches (about 19 mm) in one embodiment, or between about 0.050 inches (about 1.27 mm) and about 0.50 inches (about 12.7 mm).

Referring to FIGS. 2 and 3, the conductive human interface 100 can include one or more compliant electrodes 130 configured to make contact with the skin of the user and to receive EMG signals produced by muscles of the user or transmit electrical signals to the skin of the user. The compliant electrode 130 can be substantially even with the contact surface 124 of the insulating soft coating 120 or the compliant electrode 130 can protrude beyond the contact surface 124 of the insulating soft coating 120, i.e. the compliant electrode 130 can be embedded in the soft coating 120. The compliant electrode 130 can include a detection surface 132 shaped to promote electrical contact with the skin of the user. For example, the detection surface 132 can be domed shaped, substantially flat, concave shaped, corrugated or any other surface treatment that promotes electrical conductivity with the skin.

Generally, the compliant electrode 130 can be formed from an electrically conductive gel 134. The electrically conductive gel 134 can be formulated to such that the compliant electrode 130 has a bulk DC resistance suitable to replace metallic materials while maintaining operability. For example, titanium compliant electrodes can have a very low bulk resistivity of about 60 uΩ-m. Applicant has discovered that compliant electrodes 130 with a bulk DC resistance of less than about 1,000 Ω-cm provide a sufficient signal to noise ratio (SNR) to control a prosthesis. In some embodiments, the compliant electrodes 130 can have a bulk DC resistance of less than about 100 Ω-cm, or between about 100 Ω-cm and about 50 Ω-cm in another embodiment.

The electrically conductive gel 134 can be formed from a polymeric material that is compounded with a conductive additive 136. The polymeric material can include TPE, silicones, block copolymers, urethanes, or the like. In some embodiments, the polymeric material of the electrically conductive gel 134 can comprise a medical grade silicone such as, for example, Dragon Skin® 30 silicone by Smooth-On, Inc. of Macungie, Pa., USA. According to the embodiments provided herein, the polymeric material of the electrically conductive gel 134 can be selected based upon the elasticity of the polymeric material. For example, the Elongation at Break, according to a modified ASTM standard D412, of the polymeric material of the electrically conductive gel 134 can be less than the Elongation at Break of the insulating soft coating 120. In some embodiments, the Elongation at Break of the insulating soft coating 120 can be at least about two times greater than the Elongation at Break of the polymeric material of the electrically conductive gel 134 such as, for example, at least about three times greater. Alternatively or additionally, the Elongation at Break of the polymeric material of the electrically conductive gel 134 can be greater than about 250%, such as for example, between about 250% and about 500% in one embodiment, between about 280% and about 450% in another embodiment, or at least about 300% in a further embodiment.

The conductive additive 136 can comprise conductive materials such as, for example, gold, copper, nickel, iron, iron-oxide, silver, carbon, carbon black, carbon nanotubes, graphite, or combinations thereof. The conductive additives 136 can be provided as conductive particles, conductive strands, or both. The conductive particles can correspond to various shapes such as, but not limited to, spherical, rounded, angular, spongy, flakey, cylindrical, acicular, cubic, or the like. For example, in some embodiments, the conductive particles can be formed from amalgamated carbon nanotubes such as, for example, macro particle flakes. Suitable amalgamated carbon nanotubes include Carbon NanoStructures (CNS), which can be formed as a cross-linked and entangled arrangement of carbon nanotubes on a base material, provided by Applied NanoStructured Solutions, LLC of Baltimore, Md., USA. The cross-linked and entangled carbon nanotube within the conductive particles can have an average length of about 70 um (+/− about 20 um) with a rough thickness of about 10 um. Generally, the size of the conductive particle can be controlled by screening the particle through an orifice having a known dimension. In some embodiments, the majority of the conductive particles of the conductive additive 136 can be less than about 0.075 inches (about 1.9 mm) such, as for example, between about 0.030 inches (0.76 mm) and about 0.050 (about 1.27 mm) inches in one embodiment, less than about 0.040 inches (about 1 mm) in another embodiment. In some embodiments, the conductive particles of the conductive additive 136 can be less than about 0.075 inches (about 1.9 mm) such, as for example, less than about 0.040 inches (about 1 mm) in one embodiments, or between about in another embodiment, or between about 0.002 inches (about 50 um) and about 0.040 inches (about 1 mm) in another embodiment.

The conductive strands can be formed from one or more conductive filaments that are spun or twisted together into a substantially cord-like shape. For example, the conductive filaments can include an insulating substrate, which can be coated or embedded with electrically conductive elements such as, for example, silver, carbon, nickel, copper, gold, titanium, or the like. Substrates can include cotton, polyester, nylon, aramids, or the like. The diameter of the conductive strands can be less than about 0.006 inches (about 0.15 mm) such as, for example, less than about 0.002 inches (about 0.05 mm) in another embodiment. In some embodiments, the conductive additive 136 can comprise conductive strands having different diameters. Alternatively or additionally, the conductive additive 136 can comprise conductive strands having different coatings, substrates, or both. The length of the conductive strands can be less than about 0.2 inches (about 5 mm), such as for example, between about 0.12 inches (about 3 mm) and about 0.16 inches (about 4 mm). It is noted that, compliant electrodes 130 formed using conductive strands can produce sharp ends protruding from the detection surface 132, which can cause skin irritation. Accordingly, in some embodiments, the detection surface 132 or the entirety of the compliant electrode 130 can be formed from electrically conductive gel 134 having conductive particles without the use of conductive strands.

Referring still to FIGS. 2 and 3, the amount of the conductive additive 136 can be controlled as a weight percentage of the electrically conductive gel 134 at an uncured state. As is provided in greater detail herein, the weight percentage of the conductive additive 136 can impact the electrical and mechanical characteristics of the compliant electrodes 130. In some embodiments, the conductive additive 136 can form between about 1% and about 10% of the electrically conductive gel 134 by weight. In embodiments where the conductive additive 136 comprises the conductive particles, the conductive particles can be dispersed throughout the electrically conductive gel 134. The conductive particles can form between about 1% and about 10% of the electrically conductive gel 134 by weight such as, for example, between about 1% and about 7% of the electrically conductive gel 134 by weight in one embodiment, between about 2% and about 6% of the electrically conductive gel 134 by weight in another embodiment, or about 5% of the electrically conductive gel 134 by weight in a further embodiment.

The electrically conductive gel 134 can be provided as a moldable material, i.e., the viscosity of the material can be controlled. In some embodiments, the viscosity of the electrically conductive gel 134, in an uncured state and compounded state, can be less than about 20 million cP such as, for example, between about 1 million cP and about 10 million cP. Applicants discovered that compounding too much of the conductive additive 136 in the electrically conductive gel 134 can render the electrically conductive gel 134 difficult to mold, i.e., increase the difficulty of forming the compliant electrode 130. Specifically, the electrically conductive gel 136 can congeal into a plurality of clumps or form into a powder having an undesirably high viscosity. It is noted that viscosity can be determined using a Rubber Process Analyzer such as the D-RPA 300 available from MonTech Inc. of Columbia City, Ind., USA.

Once cured the electrically conductive gel 134, and thus, the compliant electrode 130 can be configured to maintain comfortable contact with the skin of the user for an entire day (e.g., about 18 hours). Accordingly, the hardness, the elasticity, or both of the electrically conductive gel 134 and the compliant electrode 130 can be controlled. In some embodiments, the hardness of the compliant electrode 130 can be greater than the hardness of the insulating soft coating 120. Without being bound to theory, it is believed that the increase in relative hardness can promote contact with the skin of the user. In other words, lift off can be mitigated by providing the compliant electrode 130 with greater hardness than the insulating soft coating 120, which can increase contact pressure between the compliant electrode 130 and skin of the user. The compliant electrode 130 have a hardness on the Shore 00 scale of less than about 90 such as, for example, a hardness of less than about 85 on the Shore 00 scale in one embodiment, or a hardness of between about 85 and about 30 on the Shore 00 scale in another embodiment.

Alternatively or additionally, the Elongation at Break, according to a modified ASTM standard D412, of the compliant electrode 130 can be less than the Elongation at Break of the insulating soft coating 120. In some embodiments, the Elongation at Break of the insulating soft coating 120 can be at least about 10 times greater than the Elongation at Break of the compliant electrode 130 such as, for example, at least about 15 times greater in one embodiment, or between about 15 times greater and about 25 times greater in another embodiment. Alternatively or additionally, the Elongation at Break of the compliant electrode 130 can be between about 50% and about 200%, such as for example, between about 50% and about 125% in one embodiment, or between about 75% and about 100% in another embodiment, or at least about 75% in a further embodiment. Accordingly, the compliant electrode 130 can be configured to conform and flex with the skin of the user as both move during use.

Referring collectively to FIGS. 2 and 3, the conductive human interface 100 can include a conductive path 140 for electrically connecting each of the one or more compliant electrodes 130 to another component. As used herein, the phrase “electrically connect” can mean to provide a medium for the transmission of electrical signals from one object to another object. The conductive path 140 generally includes a flexible conductor such as, for example, conductive thread, conductive fabric, conductive ink, or combinations thereof. It has been discovered, that wires may be unsuitable for use with certain embodiments of the conductive human interface 100. For example, wires can include conductors or shielding that can be substantially more rigid than the fabric layer 110, the insulating soft coating 120, or both. The difference in rigidity can damage the insulating soft coating 120, and reduce the durability of the conductive human interface 100 and cause discomfort. Additionally, the difference in rigidity can cause the wires to fatigue and lose conductivity.

In some embodiments, the compliant electrode 130 can be molded over the conductive path 140. For example, the compliant electrode 130 can be applied directly to the conductive path 140. Accordingly, the compliant electrodes 130 can make surface contact with the conductive path 140 or both the conductive path 140 and the interior surface 112 of the fabric layer 110. In some embodiments, the electrically conductive gel 134 can be applied directly to the conductive path 140 in an uncured state and cured to form the compliant electrode 130. In some embodiments, the electrically conductive gel 134 can be applied before the insulating soft coating 120 is applied. Alternatively, the electrically conductive gel 134 of the compliant electrodes 130 or the compliant electrodes 130 can be applied after the insulating soft coating 120 is applied. For example, a removable body can cover the compliant electrode sites on the conductive path 140, while the insulating soft coating 120 is applied. The removable body can then be removed to allow the compliant electrodes 130 to be applied to the compliant electrode sites. Alternatively or additionally, the compliant electrode 130 can be connected to the conductive path via a connector. For example, the connector can be formed from conductive materials such as, for example, a metal (e.g., copper, aluminum, gold, silver, etc.) or a graphite material.

The conductive human interface 100 can include an electrical connector 142 configured to electrically connect each conductive path 140 with another component. The electrical connector can include conductive members each configured to be electrically connected to one of the conductive paths 140. In some embodiments, the electrical connector 142 can be configured to transition from relatively flexible conductors to more rigid conductors. For example, the electrical connector 142 can include a separable electrical connector (e.g., pins, sockets, etc.) electrically connected to the conductive members.

Referring to FIGS. 1 and 2, in some embodiments, the conductive human interface 100 can include the prosthetic liner 102. The prosthetic liner 102 can include an umbrella 144 formed at the closed end 106 and external to the exterior surface 114 of the fabric layer 110. In some embodiments, the umbrella 144 can be formed around the electrical connector 142. For example, the umbrella 144 can be molded to the exterior surface 114 of the fabric layer 110 out of relatively hard materials such as, for example, a hard urethane.

Referring collectively to FIGS. 4 and 5, an embodiment of a conductive human interface 200 can be substantially tubular. For example, the conductive human interface 200 can extend between a first open end 204 and a second open end 206. Accordingly, the conductive human interface 200 can be provided as, for example, an arm sleeve, a leg sleeve, a wrist band, a head band, or the like. Generally, the conductive human interface 200 can include the fabric layer 110, the insulating soft coating 120, the compliant electrode 130, and the electrical connector 142, as described herein with respect to the conductive human interface 100. Additionally, the conductive human interface 200 can be formed in substantially the same way as the conductive human interface 100. In some embodiments, the electrical connector 142 can be provided on the exterior surface 114 of the fabric layer 110 between the first open end 204 and the second open end 206. Alternatively, the electrical connector 142 can be provided at the first open end 204, the second open end 206, or both.

Referring collectively to FIGS. 6 and 7, an embodiment of a conductive human interface 300 can be formed as a substantially sheet shaped body. For example, the conductive human interface 300 can have a thickness that is defined by the fabric layer 110 and the insulating soft coating 120 and demarcated by a perimeter 302. It is noted that, while the perimeter 302 is depicted in FIG. 6 as being substantially rectangular, the perimeter can be contoured to match with any desired body part. Optionally, the conductive human interface 300 can include a band 304 configured to wrap around a user and secure the conductive human interface 300 to the desired body part. Generally, the conductive human interface 300 can include the fabric layer 110, the insulating soft coating 120, the compliant electrode 130, and the electrical connector 142, as described herein with respect to the conductive human interface 100. In some embodiments, the electrical connector 142 can be provided on the exterior surface 114 of the fabric layer 110. Additionally, the conductive human interface 300 can be formed in substantially the same way as the conductive human interface 100.

Referring to FIGS. 1, 2, and 8, a processing device 150 can be operable to communicate electrical signals with the one or more compliant electrode 130. The processing board 150 can include one or more processors 152 for executing machine readable instructions to perform signal communication functions, as described herein. The term “processor” can mean any device capable of executing machine readable instructions. Accordingly, each processor can be a controller, an integrated circuit, a microchip, a signal processor, or any other device capable of implementing logic. The processing device 150 can include memory 154 communicatively coupled to the one or more processors 190 (generally depicted as double arrowed lines). As used herein, the phrase “communicatively coupled” can mean that components are capable of exchanging data signals with one another such as, for example, electrical signals via conductive medium, electromagnetic signals via air, optical signals via optical waveguides, and the like. The memory 154 described herein may be RAM, ROM, a flash memory, a hard drive, or any device capable of storing machine readable instructions.

Additionally, it is noted that the functions described herein can be provided as machine readable instructions stored on the memory 154 and executed by the one or more processors 152. The machine readable instructions can be provided in any programming language of any generation (e.g., 1GL, 2GL, 3GL, 4GL, or 5GL) such as, e.g., machine language that may be directly executed by the processor, or assembly language, object-oriented programming (OOP), scripting languages, microcode, etc., that may be compiled or assembled into machine readable instructions and stored on a machine readable medium. Alternatively, the functions, modules, and processes described herein may be written in a hardware description language (HDL), such as logic implemented via either a field-programmable gate array (FPGA) configuration or an application-specific integrated circuit (ASIC), and their equivalents. Accordingly, the functions described herein may be implemented in any conventional computer programming language, as pre-programmed hardware elements, or as a combination of hardware and software components.

In some embodiments, the processing device 150 can be configured to transform EMG signals detected by the compliant electrode 130 into control signals for an assistive device. For example, the EMG signals can be conducted from the detection surface 132 of the compliant electrodes 130 to the conductive path 140 and the processing device 150. In some embodiments, the compliant electrodes 130 can be electrically connected to high impedance differential instrument amplifiers of the processing device 150. For example, the one or more compliant electrodes 130 can have a positive contact and a negative contact. The processing device 150 can use the differential amplifier configuration to subtract common electrical noise created from the ambient environment and in electrical line oscillations from the EMG signal. Accordingly, in some embodiments, the positive and negative contacts of the one or more compliant electrodes 130 can have substantially similar bulk DC resistance values, i.e., matched bulk DC resistance values. The differential signal can then be processed for use in controlling an assistive device.

Alternatively or additionally, the processing device 150 can include device communication hardware 156 communicatively coupled to the one or more processors 152. The device communication hardware 156 can be configured to communicate, i.e., send and/or receive data signals via any wired or wireless communication protocol such as, for example, LIN bus, CAN bus, USB, FIREWIRE, IrDA, BLUETOOTH, Wireless USB, Z-WAVE, ZIGBEE, or the like. Accordingly, the one or more processors 152 can receive signals via the electrical connector 142 and transform the signals into control signals. The control signals can then be transmitted via the device communication hardware 194 to the assistive device.

Additionally, the processing device 150 can be configured to transmit electrical signals to the compliant electrode 130. For example, the electrical signals can be configured to stimulate nerve endings, create information flowing into the body, or both. In some embodiments, the processing device 150 can include a signal generator 158 configured to generate electrical signals that can be communicated to the compliant electrode 130. For example, the signal generator 158 can be communicatively coupled to the electrical connector 142 and the one or more processors 152. Accordingly, the one or more processors 152 can cause the signal generator 158 to generate the desired electrical signal. The electrical signal can be transmitted to the compliant electrode 130 via the conductive path 140 and the electrical connector 142. Alternatively, the electrical signals can be provided directly to the electrical connector 142 via the device communication hardware 156. Accordingly, in some embodiments, the signal generator 158 is omitted.

In some embodiments, the electrical signals can configured for TENS. Thus, the compliant electrode 130 can be aligned with the desired nerve ending to manage pain. For example, amputees can experience phantom limb pain, i.e., pain that is sensed as coming from an amputated limb. For example, nerve endings at the site of amputation can stimulate the brain in a manner that is interpreted as pain from the removed limb. Alternatively or additionally, the electrical signals can be transmitted to muscle or nerve endings as feedback from an assistive device. For example, amputees using assistive devices such as, for example, a prosthetic foot may have difficulty detecting uneven surfaces. Often times, the amputee may need to look directly at the assistive device in order to traverse an uneven surface. In some embodiments, the assistive device can be provided with sensors configured to detect the uneven surface such as, for example, load sensors to detect the amount and type of loading, and contact sensors configured to detect contact with the surface. In some embodiments, the sensor information can be communicated to the compliant electrode 130 as feedback that can stimulate the brain. For example, the one or more processors 152 can receive sensor data and cause the signal generator 158 to generate the desired electrical signal. The one or more processors 152 can encode the electrical signal according to the sensor data. Alternatively, the electrical signals can be provided directly to the electrical connector 142 via the device communication hardware 158.

Test Example

A test example was generated according to the embodiments described herein. Specifically, an electrically conductive gel was formed using Dragon Skin® 30 silicone as the polymeric material, and CNS particles as the conductive additive. The CNS particles were ground into a size less than or equal to about 0.040 inches (about 1 mm). The electrically conductive gel was compounded with about 5% by weight of the CNS particles. The compounded material exhibited suitable viscosity. Various comparative examples were compounded using weight percentage of conductive additives larger than the embodiments provided above. Some of the comparative examples exhibited poor manufacturability, i.e., coagulation, powdering, or inability of the silicone to cure. Once the test example cured, the electrically conductive gel exhibited suitable mechanical properties, as described above, and bulk DC resistance values between about 200 Ω-cm and about 50 Ω-cm. Some of the comparative examples exhibited poor mechanical properties such as, for example, low tear strength, crumbling, and biological incompatibility.

It should now be understood that the embodiments described herein can provide compliant electrodes that can reliably communicate electrical signals with the skin of a user without causing discomfort when worn throughout the day. For example, compliant electrodes can be formed from electrically conductive gel that provide relatively soft and flexible electrodes compared to metallic electrodes. Moreover, the complaint electrodes can be configured to maintain contact with the skin of the user and mitigate lift off.

It is noted that the terms “substantially” and “about” may be utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter. 

What is claimed is:
 1. A conductive human interface, comprising: an insulating soft coating; and one or more compliant electrodes embedded in the insulating soft coating, wherein the one or more electrodes are formed from an electrically conductive gel, the electrically conductive gel comprises a polymeric material and conductive particles dispersed in the compliant material, and the conductive particles form between 2% and 6% of the electrically conductive gel by weight.
 2. The conductive human interface of claim 1, wherein the one or more compliant electrodes have a bulk DC resistance of less than 1000 Ω-cm.
 3. The conductive human interface of claim 1, wherein the polymeric material comprises silicone.
 4. The conductive human interface of claim 1, wherein the conductive particles are formed from amalgamated carbon nanotubes.
 5. The conductive human interface of claim 1, wherein a majority of the conductive particles is less than about 0.075 inches in size.
 6. The conductive human interface of claim 1, wherein the hardness of the one or more compliant electrodes is greater than the hardness of the hardness of the insulating soft coating.
 7. The conductive human interface of claim 6, wherein the hardness of the one or more compliant electrodes is between about 85 and about 30 on a Shore 00 scale.
 8. The conductive human interface of claim 1, wherein the polymeric material of the electrically conductive gel has a lower Elongation at Break than the insulating soft coating.
 9. The conductive human interface of claim 1, wherein an Elongation at Break of the insulating soft coating is at least 10 times greater than an Elongation at Break of the one or more compliant electrodes.
 10. The conductive human interface of claim 9, wherein the Elongation at Break of the one or more compliant electrodes is between about 50% and about 200%.
 11. The conductive human interface of claim 1, wherein the one or more compliant electrodes comprises a positive contact and a negative contact, and wherein the positive contact and the negative contact have matched bulk DC resistance.
 12. The conductive human interface of claim 1, comprising a fabric layer having an interior surface and an exterior surface, wherein the insulating soft coating and the one or more compliant electrodes are applied to the interior surface of the fabric layer.
 13. The conductive human interface of claim 12, comprising: a conductive path electrically connected to the one or more compliant electrodes; and an electrical connector electrically connected to the conductive path.
 15. The conductive human interface of claim 1, wherein the conductive human interface forms a liner, a sleeve, or a pad.
 15. A conductive human interface, comprising: an insulating soft coating; and one or more electrodes embedded in the insulating soft coating, wherein the one or more electrodes are formed from an electrically conductive gel, the electrically conductive gel comprises a compliant polymer and amalgamated carbon nanotubes dispersed in the compliant material, and the amalgamated carbon nanotubes are less than about 0.040 inches in size.
 16. The conductive human interface of claim 15, wherein the amalgamated carbon nanotubes form between 1% and 7% of the electrically conductive gel by weight.
 17. The conductive human interface of claim 15, wherein the one or more compliant electrodes have a bulk DC resistance of less than 1000 Ω-cm.
 18. The conductive human interface of claim 15, wherein the polymeric material comprises silicone.
 19. The conductive human interface of claim 15, wherein the hardness of the one or more compliant electrodes is greater than the hardness of the hardness of the insulating soft coating.
 20. The conductive human interface of claim 19, wherein the hardness of the one or more compliant electrodes is between about 85 and about 30 on a Shore 00 scale.
 21. The conductive human interface of claim 15, wherein an Elongation at Break of the insulating soft coating is at least 10 times greater than an Elongation at Break of the one or more compliant electrodes.
 22. The conductive human interface of claim 21, wherein the Elongation at Break of the one or more compliant electrodes is between about 50% and about 200%.
 23. The conductive human interface of claim 15, wherein the conductive human interface forms a liner, a sleeve, or a pad.
 24. An electrically conductive gel, comprising: a polymeric material; and a conductive additive compounded with the polymeric material, wherein: the conductive additive comprises conductive particles, the conductive particles form between about 1% and about 10% of the electrically conductive gel by weight, a majority of the conductive particles is between about 0.030 inches and about 0.050 inches in size; an Elongation at Break of the electrically conductive gel is between about 50% and about 200%, and the electrically conductive gel has a bulk DC resistance of less than 500Ω.
 25. The electrically conductive gel of claim 24, having a viscosity between about 1 million cP and about 10 million cP, when the electrically conductive gel is in an uncured and compounded state. 